The present invention relates to an optical recording/reproducing apparatus for performing recording,reproduction and erase of signals and more particularly to an optical recording/reproducing apparatus provided with an optical correction means for stably positioning an optical spot at a predetermined position.
In the past, proposed as an optical recording/reproducing apparatus for irradiating two or more light spots on an optical recording medium by means of an objective lens are, for example, an apparatus in which a signal is recorded and reproduced by one light spot and erasing is effected by another light spot and an apparatus in which a signal already recorded is erased by one light spot while a new signal is recorded concurrently by the one light spot and recorded signal is reproduced by another light spot.
The optical recording/reproducing apparatuses described above require a light spot relative position correction means for maintaining the relative position between the two light spots highly accurately and stably. For example, JP-A-62-92144 discloses a method for realization of this type of relative position correction means.
According to the aforementioned method, for one of two light spots (hereinafter referred to as a first light spot), a reflection light beam from an optical recording medium is led to a predetermined photodetector to produce a tracking signal based on which an objective lens is moved to perform tracking control. At that time, for the other light spot (hereinafter referred to as a second light spot), a reflection light beam from the optical recording medium is led to another photodetector to produce a tracking signal based on which a wedge-shaped prism disposed immediately after a collimating lens is rotated in order that the deflection angle of a light beam (hereinafter referred to as a second light beam) passing through the prism and reaching the objective lens is controlled to perform position correction through which the relative position of the second light spot to the first light spot can always be kept to be constant.
Accordingly, through the use of the relative position correction means as above, accuracy of irradiation positions can be maintained for each of the plurality of light spots. Additionally, the sensitivity of the inclination angle of the light beam to the rotation angle of the wedge-shaped prism can be designed to be sufficiently low and therefore correction which is stable against external shock can be ensured.